High resolution recording and display



ec. il, 1962 F. D. covELY 3RD, ETAL 3,063,455

HIGH RESOLUTION RECORDING AND DISPLAY 4 Sheets-Sheet l Filed June 6,1957 INVENToRs FRANK D. EmzELY, EBD. BY Dumm J. PARKER ec. l1, i962 F.D. covELY 3RD, ETAL 3,063,465

HIGH RESOLUTION RECORDING AND DISPLAY 4 Sheets-Sheet 2 Filed' June 6,1957 Dec. 11, 1962 F. D. covx-:LY 3RD, ETAL 3,068,465

HIGH RESOLUTION RECORDING AND DISPLAY 4 Sheets-Sheet 5 Filed June 6,1957 INVENToRs FRANK D. Envzmnn. BY Dumm-1.1:: J. PARKER iffJI/Vly Dec.11, 1962 F. D. covl-:LY 3RD, ETAL 3,068,465

HIGH RESOLUTION RECORDING AND DISPLAY 4 Sheets-Sheet 4 Filed June 6,1957 INVENToRs FRANK D. EDVELYRD# By DDNALD J. PARKER 3,05%,465 PatentedBec. ll, 1962 3,068,465 HGH RESOLUTIQN RECRDENG AND SHSPLAY Frankl).Covely 3rd, Haddonieid, and Donald E. Pariser, Camden, NJ., assignors teRadio Corporation of America, a corporation of Belaware Filed 6, 1957,Ser. No. 65915838 17 Ciaims. (Cl. 343-5) The purpose of this inventionis to solve the problem of displaying and recording high resolutionelectrical signals. While not restricted thereto, the invention is parFticularly applicable to high resolution radar systems which providetarget range information accurate to several feet.

In the discussion which follows, reference will be made to the radar artas a specific example of where the present invention may be used. lt isto be understood, however, that the invention is applicable to numerousother types of systems in which high resolution electrical signalinformation is available which must be displayed and/or recorded. Forexample, the system is applicable to facsimile, special types oftelevision recording systems, etc.

For the purpose of illustration, assume that it is required to recordand display radar data in an aircraft, ying at a speed of 600 miles perhour, which transmits radar pulses in a directionperpendicular to itsline of flight. The radar range data has a resolution of feet, that is,the data is of sufficient accuracy to determine the range of an objectwithin plus or minus 5 feet. The :range of interest is miles. Thedisplay resolution required is 20 milesX 6000 feet per mile v 5 reet or24,000 lines, in television parlance. (The approximation l nauticalmiler-6000 feet is used to simplify the mathematics.) The informationfor each scan line is received in 20 miles l2 microseconds/miles=240microseconds. During the time the information is being received, theaircraft is moving forward at a speed of 600 milesV per hour, orapproximately 1000 feet per second. For equal resolution in thedirection that the aircraft is ying, it should move not more than 5 feetduring one scan interval. Thus, the minimum pulse repetition frequencywhich can be employed is 1000/ 5 :200 cycles per second. The pulserepetition period is therefore l/200 or 5000 microseconds.

A cathode ray tube cannot be used to display information of the abovehigh degree of resolution. The best resolution obtainable to date, tothe writers knowledge, is about 2000l lines, and this at extremely lowlight intensity. For acceptable display, the resolution must besubstantially increased, and the light output of the cathode ray tubemust be increased.

Another approach to the problem is to. attempt to record the radar datadirectly on a permanent medium such as lm or electrofax paper. Here, therecording medium, if of sufficient size does have the resolutionrequired to record the information. However, the recording medium mustbe of high sensitivity. Also, the light source which excites the lm orpaper must be of high intensity, must be capable of being modulated at100 megacycles or more, and must be scanned at the radar sweep speed(240 microseconds). These requirements appear to be insurmountable atthe present state of the art.

According to the present invention, the incoming high resolutioninformation is first applied to a device, the inher-ent resolution ofwhich is much lower than that of the incoming signals. ln a preferredform of the invention, the signals are applied to a storage tube, Animportant advantage of. using the storage tube is that it is capable ofrecording even short duration signals at extremely high intensity. Onepractical tube, for example, is capable of recording a 1 microsecondsweep at full brilliance. However, the disadvantage of the storage tubeis that its resolution is relatively low-about 500 lines, at the presentstate of the art. This disadvantage is overcome according to theinvention by spreading the writing of the incoming information along aplurality of lines on the storage tube screen. Thus, if the inherentresolution is 500 lines and the incoming information is written on 40lines, the resultant overall resolution is 20,000 lines.

The procedure described above solves several problems inherent in therecording of high resolution information. However, it introduces a newproblem in that the information now on the screen of the storage tube isnot in useable, that is, legible or understandable, form. According tothis invention, the information on the storage tube is projected by anoptical system onto a moving recording medium such as a relatively widestrip of moving electrofax paper. The optical system combines theseparate lines end-to-end on the recording medium so that the recordedimage corresponds to the high resolution electrical information.

Returning for a moment to the specific example discussed in theintroductory portion of this application, the range of interest is 20miles. This corresponds to 240 microseconds. In other words, theincoming information is written on the storage tube in 240lmicroseconds. The pulse repetition interval is roughly 5000microseconds. This means there are approximately 4760 microseconds eachcycle available for recording the information written on theV storagetube. With the brightness available from the direct view storage tube,the recording can be done directly on the electrofax paper with anexposure of about 500 microseconds. The forward motion of the aircraftin 500 microseconds is about 0.5 foot so that the smear resulting fromthe motion of the paper (which moves at a speed related to that of theaircraft) is negligible.

Erasure of the storage tube can be accomplished during the remainder ofthe pulse repetition interval, that is, during the remaining 4240seconds before the next transmitted pulse.

If the pulse repetition rate is increased, say 5 to l0 times, anordinary cathode ray tube can be used instead of the storage tube. Theincrease in pulse repetition rate increases the number of times theimage is written on the cathode ray tube screen during the time theaircraft moves tive feet, and this increases the intensity of the imagewritten on the screen.

The invention will be described in greater detail by reference to thefollowing description taken in connection with the accompanying drawingin which:

FIGURE 1 is a block circuit diagram of a preferred form of theinvention;

FlGURE 2 shows waveforms present at various points in the circuit ofFIGURE l',

FIGURE 3 is a more detailed showing of an optical system which may beused in the arrangement of FIG- URE 1; and

FIGURE 4 is a schematic circuit diagram of a portion of the circuitshown in FGURE l.

ln the figures similar reference numerals are applied to similarelements.

Referring to FGURE l, the source of high resolution signals isindicated` by block l0. The source may, for example, bea radar systemand the video output signals are available at leads 12 and 13. Thesesignals are appliedthrough video amplier 14 to the writing gun grid ofstoragetube 16. TheV video information a at lead i7 is shown in FIGURE2:1. The first pulse is the transmitted pulse, and the remainder of thesignals are noise and echoes.

Triggerpulses from the source l0 are applied over lead lthrough aphantastron gate circuit 25 to a gated oscillator 26. Details of asuitable oscillator are shown in aoeaaee o FIGURE 4, which is discussedin more detail later, and in volume 19 of the Radiation LaboratorySeries at pages 226-235. Details of a suitable phantastron circuit aregiven in the same volume at pages 195-200. (In the discussion whichfollows, various pages of volume 19 of the Radiation Laboratory Serieswill be made reference to.) The output of the phantastron is a squarewave b. The output of gated oscillator 26 consists of a gated sine wavec. These waves and others to be discussed below are shown in FIGURE 2.

The sine wave of stage 26 is applied to a bistable multivibrator 27 andto a sine wave synchronized, free running multivibrator 27a. The outputof the latter is a wave e having a short negative duty cycle.

The square wave output d of the bistable multivibrator 27 is applied tothe horizontal writing deflection generator 20, which producestriangularly shaped wave f. Wave f, in turn, is applied to thehorizontal deflection means of storage tube 16. A deflection wave ofthis type rst deects the electron beam from left to right and then fromright to left, etc. A suitable triangular wave sweep circuit is shown inFIGURE 4.

Referring briefly to FIGURE 4, the gated oscillator 26 consists of agate stage 16 followed by a Hartley oscillator 1&2. -The gate stage155i) is driven to cut olf during the negative-going portion of gate b.During this interval the Hartley oscillator 162 produces the sine wavec. However, upon the termination of the negative gate b, gate tube 160begins to conduct heavily and this biases the Hartley oscillator to cutolf.

The sine wave c is applied to bistable multivibrator 27 and controls theoperating frequency of the bistable multivibrator. Square wave dgenerated by the bistable multivibrator has a period which correspondsto a period of the triangular wave. In other words, the upward excursionof the square wave corresponds to the upward excursion of the sawtoothwave and the downward eX- cursion of the square wave to the downwardexcursion of the sawtooth wave.

The triangular wave generator 2G consists of a pair of seriallyconnected pentodes 104, 106. The pentodes are balanced in such mannerthat the upper one 104 conducts twice as much as the lower one 106. Withthe upper pentode 104 conducting (due to the upward excursion of thesquare wave) the charging capacitor S goes positive due to conduction ofelectrons from it at a constant rate. On the next excursion (downward)of the square wave, the upper pentode is cut olf. Now the chargingcondenser 108 goes negative (at a constant rate) because Vthe electronsowing through the lower pentode are collected by it. Clamper diodes 110and 112 are conventional.

Wave d is available at point 114 in the circuit of FIG- URE 4. Returningnow to FIGURE l, wave d is applied to the Vwriting vertical deliectionwave generator 22 which produces a step type wave g. A suitablegenerator is shown in volume 19 at pages 293-294. This wave is appliedto the vertical deflection means of the storage tube and it causes thesucceeding horizontal sweeps to be written, one beneath theV other.

In order to prevent distortion at the beginning of each vertical step,the wave e (from stage 27a) is applied to the video amplifier 14. Hereit acts as a blanking signal.

The erasure stages for the storage tube are similar to the writingstages. The input signals from lead 13 are applied to a phantastrondelay circuit 23 which inserts a delay suicient to permit theinformation written on the storage screen to be recorded. The delay, forexample, may be on the order of 500 microseconds or so. The delayedpulses derived from the radar transmitter pulses are applied to a gatedoscillator 29 which is similar to oscillator 2,6. The gated sine wavesignals from oscillator 29 are applied to a bistablemultivibrator 31which is similar to bistable multivibrator 217. Bistable multi- Vibrator31 triggers the erasing horizontal deflection circuit 3@ which issimilar to circuit 2t), and the erasing vertical deflection circuit 32which is similar to circuit 22. The output waves z', j and k of thestages just discussed are shown in FIGURE 2.

Erasure stage 34 consists of a bistable multivibrator. It is turned onby pulses from phantastron delay oscillator 23 and turned off by pulsesfrom source 1i). The erasure blanking voltage iz which consists of asquare wave signal, is applied to the erasing gun grid of the storagetube.

High voltage pulser 36 consists of a second bistable multivibrator. Itis turned on from the pulses from phantastron delay oscillator 28 andturned off by pulses from source 1G. The function of the high voltagepulser 36 is to prevent light from being emitted from the storage tubeduring the erasure interval. During this interval, the high voltage b isreduced in amplitude as is shown in FIGURE 2l.

As already mentioned, waves f and g from the writing horizontal andvertical deflection generators 20 and 22 are applied to the horizontaland vertical deection means, respectively, of the storage tube 16.Horizontal and vertical erasure voltages j and k are applied to thehorizontal and vertical erasing beam deflection means of storage tube16.

he light'emitted from the storage tube is focused by an optical system38 onto a moving recording medium 4i). The optical system is describedin further detail later in connection with FIGURE 3. The recordingmedium may be film' but preferably comprises sensitized electrofaxpaper. The paper is driven by a motor 42 and gears 44. The motor speedis preferably synchronized with the aircraft speed by applying power tothe motor from source 46, the magnitude of the power being proportionalto the aircraft speed.

FIGURE 3 shows the face 56 of storage tube 16. For the'purpose of thisillustration, it is assumed that each line of incoming radar informationis written on the storage `tube screen as three lines. This effectivelyincreases the resolution of the storage tube from 500 lines to 1500lines. In the illustration, the lines are written vertically. Numbersare applied to the ends of the lines to show the direction in which theyare written. Thus, lines 1, 2 and 3, 4 are written from' top to bottom,as viewed in the drawing, and the middle line 2, 3 is written frombottom Vto top.

Line l, 2 is optically focused onto the moving electrofax Vpaper 40 byan optical system including mirror 52, lens 54, reversing prism 56 andmirror 58. The middle line is projected onto the moving electrofax paperin end-to-end alignment with the first line by mirror 60 and lens 62.The last line 3, 4 is optically focused onto the moving electrofaxpaperrby an optical system 64 which is analogous to the optical systemwhich projects the first lines onto the paper. As can be seen in FIGURE3, the optical system focusses the three separate lines on the storagetube screen into a single line, the segments 1 2, 2 3 and 3-4 of whichare in the same alignment as the incoming video information. OpaqueVmembers 63 are to mask the electrofax paper and thereby to prevent itfrom lgeing exposed by images other than the ones on the screen Itshould be appreciated that although the incoming information isdisplayed in three lines on the storage tube of 240 lines may be writtenon the screen. This would increase the resolution of the storage tubescreen from SOO to '120,000'.` However, 240 lines would require a fairlyinvolved optical system. As a practical matter, vit is preferable tomaintain the number of lines on the storage tube screen to about Z0 orless with storage tubes of the size presently in use (l0"screens).

The -moving recording medium (electrofax paper, in the example above)must be moved at the proper speedrelative to the aircraft speed in orderfaithfully to reproduce the image. The ratio of paper speedto aircraftspeed is dependent upon the scale of the image displayed on the cathoderay tube. As a simple example, if the aircraft speed is 1() miles perminute and the scale of the display on the cathode ray tube is miles tothe inch, the paper speed must be l inch per minute if the magnificationof the imaging optical system is l to 1. Of course, in a practicalsystem, a distance much smaller than 10 miles is displayed on l inch ofthe cathode ray tube so that, in a practical system, the speed of themoving paper is substantially greater than l inch per minute, assumingan aircraft'speed of l0 miles per minute and 1 to l magnification in theoptical system. Variation in the relative speeds of the paper andaircraft introduce distortions into the image on the paper.

The mechanism for controlling the speed of the paper is conventional andmay be the same as that used for line exposure of camera films. Forexample, servo mechanism drives may be used for the paper which operateon information supplied by the air speed indicator or, in more elaboratesystem, on information supplied by ground speed measuring devices of thephoto-electric or radar type.

The present invention is applicable to cases in which succeeding linesof the incoming radar information are similar, for example, casesanalogous to A type radar displays or to cases in which succeeding linesof information are different, for example, cases in which the incominginformation is like that received during a B type display or in whichthe incoming information consists of a television picture or succeedinglines of a photograph.

What is claimed is:

1. A recording system comprising, in combination, connections for asource of high resolution electrical signals; display means having aninherent resolution along one dimension of the screen thereof which is afraction of the resolution of said signal; means connected to saidconnections and to said display means for dividing the signal into aplurality of successive parts and writing each part of the signal on adifferent one of a plurality of lines on the screen of the displaymeans; a recording medium; and means for projecting the informationdisplayed on the display means onto the recording medium with thedisplayed lines in end-to-end alignment.

2. A recording system comprising, in combination, connections for asource of high resolution electrical signals; display means having aninherent resolution along one dimension of the screen thereof which is afraction of the resolution of said signal; means connected to saidconnections and to said display means for writing successive parts ofthe electrical signal along respective successive ones of a. pluralityof lines of the screen of the display means parallel to said onedimension; a recording medium; and means for projecting the informationdisplayed on the display means onto the recording means with thedisplayed lines in end-to-end alignment.

3. A recording system as set forth in claim 2 in which the means forwriting the electrical signal along a plurality of lines of the screenof the display means includes means for writing adjacent ones of saidlines in opposite directions.

4. A recording system comprising, in combination, connections for asource of high resolution electrical signals; display means having aninherent resolution along one dimension of the screen thereof which is afraction of the 5 resolution Vof said signal; means connected to saidconnections and to said display means for writing successive parts ofthe electrical signal along respective successive ones of a plurality oflines of the screen of the display means parallel to said one dimension;a recording medium; and o-ptical means for projecting the information`displayed on the display means 'onto the recording means with thedisplayed lines in end-to-end alignment.

5. A recording system comprising', 'in combination, connections for asource of high resolution yelectrical signals; a direct view storagetubehaving an inherent resolution along one ydimension of the screenthereof which is a fraction of the resolution of said signal; meansconnected to said connections and to said storage tube forwriting'successive parts of the electrical signal along respectivesuccessive ones of a plurality of lines on the storage tube screen; arecording medium; and means for projecting the information displayed onthe storage tube screen onto the recording medium with the displayedlines in end-t0- end alignment.

6. A recording system as set forth in claim 5, wherein the recordingmedium consists of electrofax paper.

7. A recording system as set forth in claim 6, and further includingmeans for moving the electrofax paper in such manner that successivelines of the information recorded thereon do not overlap one another.

8. A radar system comprising a transmitter for transmitting radarpulses; a receiver for receiving ech-o pulses;

direct view storage tube means operatively associated with the receiverfor displaying the echo pulses received during each reception intervalalong a plurality of lines of the screen of the storage tube; arecording medium; and optical means in operative relation with thestorage tube for projecting the lines on the screen onto the recordingmedium in end-to-end alignment.

9. A system as set forth in claim 8 in which the recording mediumcomprises electrofax paper.

10. A system as set forth in claim 8 in which the radar system islocated in a moving vehicle, and further including means in operativerelation with the recording medium for moving the same at a speedrelated to the speed at which the vehicle moves.

1l. In combination, a display device on the screen of which electricalsignals may be displayed, a recording medium having a resolutionsubstantially higher than that of said screen; means for displayingsuccessive parts of the signal along successive ones of a plurality oflines on said screen; and means for projecting the lines on the screenon-to sai-d medium in end-to-end alignment.

12. A recording system comprising, in combination, connections for asource of high resolution electrical signals; display means having aninherent resolution along one dimension of the screen thereof which is afraction 1of the resolution of said signal; means for displayingsuccessive parts of said signal along successive ones of a plurality oflines on the screen of the display means; a recording medium; and meansfor projecting the information displayed on the display means onto therecording medium with the displayed lines in end-to-end alignment.

13. in combination, a display means having a screen on which electricalsignals may be written, a recording medium having a resolutionsubstantially higher than that of said screen along the largestdimension across said screen, connections for incoming electricalsignals, means for writing said signals on said screen along a pathhaving a length which is substantially greater than said largestdimension, and means for optically transferring the signals written onthe screen onto a recording medium in a substantially straight line.

14. The invention according to claim 13 wherein said path comprisesdiscrete traces one alongside the other.

15. ln combination, a display means having a screen on which electricalsignals may be Written, a recording medium having a resolutionsubstantially higher than that of said screen along the largestdimension across said screen, connections for electrical signalsoccurring in time sequence, means for Writing said signals on saidscreen in said time sequence along a path having a length Which issubstantially greater than said largest dimension, and means foroptically transferring the signals Written on the screen onto arecording medium in a substantially straight line and With the signalsin position sequence corresponding to said time sequence.

16. A recording system comprising, in combination, connections for asource of high resolution electrical signals; a cathode ray tube havingan inherent resolution along the largest dimension across the screenthereof which is a fraction of the resolution of said signal; means forWriting successive parts of said signal along successive ones of aplurality of cathode ray traces on the screen of the cathode ray tube;said plurality of cathode ray traces having a total length when placedin end-toend alignment Vthat is substantially greater than said largestdimension across the screen; a recording medium; and means for opticallytransferring the information written on the cathode ray tube onto therecording medium with said cathode ray traces end-to-end in a straightline.

17. In combination, a cathode ray tube having a screen across which theelectron beam of the tube may be deilected to produce a trace of light,an image receiving medium having a resolution substantially higher thanthat of said screen along the largest dimension across said screen,means for detlecting said beam to produce -a trace of light along a pathon said screen having a length which is substantially greater than saidlargest dimension, and means for optically transferring said trace oflight onto said image receiving medium in a substantially straight linewith successive portions of the resulting straight line trace of lightoccurring in the sequence in which the cor responding portions occur onsaid screen.

References Cited in the le of this patent UNITED STATES PATENTS2,415,981 Wolff Feb. 18, 1947 2,422,295 Eaton June 17, 1947 2,430,307Smith Nov. 4, 1947 2,549,072 Epstein Apr. 17, 1951 2,725,554 PhillipsNov. 29, 1955 2,727,428 Herman Dec. 20, 1955

